Offered Talk Session: Capturing the human gut volatilome: non-destructive, continuous VOCs detection during colonic in-vitro fermentation

Background: Current human gut metabolomic research focuses on microbial non-volatile metabolites (conventional metabolome), leaving volatile organic compounds (VOCs) as a missing component [1,2]. Objective: This research effort intends to provide more in-depth information on how gut microbiota metabolize food components during fermentation by merging non-invasive, continuous analytical approaches with in-vitro gut simulator to track the time evolution of small molecules released by gut microbial consortium into the headspace [3,4]. Methods: Due to their complementary analytical capacities, two techniques are presented for efficient separation and identification of analytes and rapid quantitative analysis without sample preparation [2]. The proposed approaches in this investigation are automated Head-space Solid Phase Micro Extraction coupled with Gas Chromatography-Mass Spectrometry (HS-SPME-GC-MS) and Proton Transfer Reaction Time of Flight Mass Spectrometry (PTR-ToF-MS). The goal is to link GC-MS profiling with PTR-ToF-MS untargeted detection to be able to track a subset of masses of interest to reveal concentration change during gut fermentation [3]. Results: The anaerobic in-vitro gut fermentation performed directly in 20mL vials followed over 24 hours by HS-SPME-GC-MS and PTR-ToF-MS was able to detect the release in time of several short chain fatty acids (SCFAs) and medium chain fatty acids (MCFAs) derived from 24h oat bran fermentation. The detected acids were co-released after 4 hours of fermentation and their relative abundance increased in time. The information collected can be used to analyse the dynamics of bacterial foraging on complex undigestible food substrates to gain new mechanistic insights on the gut bacterial ecosystem. [1] Weisskopf, L., Schulz, S., & Garbeva, P. (2021). Microbial volatile organic compounds in intra-kingdom and inter-kingdom interactions. Nature Reviews Microbiology, 19(6), 391-404. [2] Meredith, L. K., & Tfaily, M. M. (2022). Capturing the microbial volatilome: an oft overlooked'ome'. Trends in Microbiology, 30(7), 622-631. [3] Biasioli, F., Gasperi, F., Yeretzian, C., & Märk, T. D. (2011). PTR-MS monitoring of VOCs and BVOCs in food science and technology. TrAC Trends in Analytical Chemistry, 30(7), 968-977. [4] Pérez-Burillo, S., Molino, S., Navajas-Porras, B., Valverde-Moya, Á. J., Hinojosa-Nogueira, D., López-Maldonado, A., ... & Rufián-Henares, J. Á. (2021). An in vitro batch fermentation protocol for studying the contribution of food to gut microbiota composition and functionality. Nature protocols, 16(7), 3186-3209.